1. Field of the Invention
The present invention relates to a practical, economical, and convenient method of forming foundation structures. More particularly, the preferred invention hereof relates to a method of forming foundation piles and pile caps.
2. Description of the Prior Art
In the construction of large buildings such as multi-story office buildings and other heavy structures, it is necessary to first provide a firm foundation. A typical foundation may comprise a number of footers. Each footer may typically include a plurality of columnar foundation piles supporting a pile cap which provides a base for the main structural components of the structure.
Patent No. 3,228,200 illustrates a commonly employed method for forming foundation piles. As disclosed in the '200 patent, a flighted auger with a hollow shaft is inserted, that is, bored or drilled into the soil, until the lower end of the auger is at the desired depth. Advantageously, this depth is at the level of bedrock or of sufficient depth to provide stable support for the pile and the building to be supported thereby. Pumpable grout is then discharged through the lower end of the auger shaft as the auger is moved upwardly so that the displaced soil is replaced by the grout until the top surface thereof is generally even with the initial grade of the soil. The grout so placed forms the foundation pile. Typically, a number of piles are constructed near one another in order to form a pile cluster.
It often happens, however, that the upper surface of the pile, which is generally even with the initial grade of the soil, is above the final desired bottom level of the pile cap to be supported by the pile. In such an event, the soil is removed in the vicinity of the pile down to the desired new grade level. That portion of the pile extending above the new grade level must then be removed by jackhammering or sawing so that the upper surface of the pile is generally adjacent the new grade level. The pile cap, typically formed of concrete, is then poured on top of the foundation pile. As those skilled in the art will appreciate, the process of cutting down the pile to the lower grade level is laborious, time consuming and expensive.
To solve this problem, some builders manually dip or remove grout from the newly formed pile before it hardens down to the desired grade level. This is also laborious, time consuming, and expensive and is particularly awkward when a reinforcing bar cage has been placed in the grout.
As an alternative, it may sometimes be possible to remove the soil in the vicinity of the planned foundation pile down to the level of the final grade before the foundation pile is formed, thus obviating the need for dipping the grout or later cutting down the the pile to the desired height. This may not be practical, however, because by removing the soil large holes are created throughout the construction site at the location of each pile or pile cluster. This in turn presents a hazard to vehicles operating on the construction site, or may prevent the use of some vehicles entirely, such as cranes or the like. Additionally, such holes collect water which must be pumped out before pouring of the pile cap, again adding additional labor and expense to the construction process. Furthermore, even if the grade is initially lowered in the vicinity of the planned pile(s), the soil displaced from the pile size as an auger bores the hole for the pile at least partially fills up the hole which then requires the use of a backhoe or the like to remove the displaced soil to again reestablish the desired grade level. The net result is that it is less expensive to pour the pile to the initially higher grade where the soil can be more conveniently removed by an end loader or the like, and then to later lower the grade level and cut down the height of the pile to the desired level.
Thus, the prior art points out the need for a method of forming concrete piles and pile cap which reduces the labor, time, and expense of known methods.